1 Background/Rationale: The premise of this grant is that despite the potential importance of antibodies in the 2 prevention and control of HIV infection, the lack of durability in the anti-HIV gp120 response is a problem for 3 HIV vaccine development that threatens their potential utility. 4 5 Objectives: Our hypothesis is that quantitative and qualitative differences between the long-lived plasma cells 6 that make anti-HIV Env antibodies compared to those that do not. We have recent and detailed data from a 7 number of HIV-infected individuals from whom we have obtained detailed bone marrow repertoire data, 8 identifying and isolating the predominant antibodies in circulation. Knowing which antibodies constitute the 9 repertoire allows us to identify and track the antibody secreting cells in the various plasma cell compartments. 10 Doing this, we have identified that plasma cells, including long-lived plasma cells, that produce anti-gp120 11 antibody can indeed be found in the bone marrow patients with chronic HIV infection. The specific aims of this 12 proposal are 1) Compare the transcriptional profile of bone marrow long-lived plasma cells secreting anti- 13 gp120 antibodies to non-gp120 long-lived plasma cells; 2) Compare phenotypic differences between bone 14 marrow long-lived plasma cells secreting anti-gp120 antibodies to non-gp120 long-lived plasma cells; 3) 15 Determine the effect of cART treatment on anti-Env antibody secreting plasma cells in the bone marrow. 16 17 Methods: We plan on studying the plasma cells from several different groups of individuals: chronic HIV 18 infected, HIV-infected on cART, and normal volunteers who have been vaccinated in the IHV01 HIV vaccine 19 studies. Bone marrow samples will be sorted into four populations based on CD19 and CD138 expression. The 20 first step is to define the anti-gp120, anti-gp41, anti-p24, and anti-diphtheria bone marrow repertoire in the 21 donors (6 chronically infected pre and post-cART and 6 HIV vaccinee donors). Thereafter the cell signatures 22 (transcriptome) amongst the various antigen-specific plasma cells will be compared with each other, across 23 plasma cell subsets, and cohorts. Next, the phenotypic differences (clonal frequency, Elispot, secretion rates) 24 will be measured and then compared between groups, as above. Using paired samples before and after cART 25 therapy, we will study the effects of cART on the transcriptome and phenotypic profile of the plasma cell 26 subsets. We will also determine if the anti-gp120 long-lived plasma cells seen in HIV infection are ?transient? 27 (disappear with cART), and whether a ?true? long-lived population can be seen in HIV infection or vaccination. 28 29 Impact: We propose that the studies above will elucidate the nature of the antibody longevity defect against 30 HIV-1 gp120, which will have direct implications for HIV vaccine design.